The number of beds have nothing to do with the production of creatures, but it do help you when battle breaks loose. Because then you need beds to hospitolize wounded creatures so that they don't just dies.

Certain buildings in the dungeon increase the production rate of a creature. For example, I think the Orc status increase the orc production a lot. If you hover buildings you will see a +X% with a creature icon beside it in the info bar. This is the production rate.